1. Field of the Invention
The present invention relates to communications networks, and, more particularly, to a method and apparatus for detecting the presence or absence of devices connected to communications networks.
2. Description of Related Art
Computer networks (such as Ethernet networks, for example) often use peripheral devices connected to a management workstation. In such networks, management hardware or software, or both, can typically detect the presence or absence of peripheral equipment only when the equipment is powered on and at least partially functional, since detection is done by recognizing received data having a known format. For example, standard Ethernet interfaces use link pulses and carrier sense for detecting equipment presence. Thus, standard detection schemes may require hardware on both ends of a communication link to have power; functional network interfaces; and good cables and connections. If a problem exists, it may be difficult to distinguish whether the cause is a bad cable, a bad connection, an unpowered device, a bad Ethernet interface, or another problem.
In commercial networks, gathering diagnostic information for equipment may require sending specially trained personnel to a remote site even if the “problem” is simply an unplugged or missing circuit board or piece of equipment. Even in cases where network devices are co-located with management devices in equipment racks, many presence detection systems cannot narrow possible problems, which can slow troubleshooting efforts. In addition, in home networks, non-technical users may find it more difficult to get adequate troubleshooting assistance if they cannot isolate the cause of a problem at a basic level. Accordingly, there is a need to more easily detect whether peripheral communications equipment is installed, powered on, or unplugged, even if the equipment is not functional or is only partially functional.